PHPA is a partially hydrolysed
polyacylamide of medium molecular weight. PHPA is a water soluble encapsulating
polymer which is used to stabilize hydratable and dispersible claystone. PHPA
is supplied as a powder.

Application

PHPA can be added to water based drilling
muds o its own or in combination with KCL, to inhibit shale bearing formation.
Due to PHPA’s encapsulating property, clay and shale problems such as sloughing
and bit balling are effectively prevened. PHPA reduce uncontrolled build up of
colloid solid and thus ensures control of viscosity at high penetration rate.
This effect of PHPA on viscosity, decreases in high salt concentration. PHPA
loses it’s effectiveness at higher calcium and magnesium ion concentration.
These bi – valent cations should be kept to minimum with Soda ASH.

Recommended treatment

PHPA is added to obtain good solids control
and stability of the well bore and should be add on regular basis. Treatment of
1.5 to 10 kg/m3 (0,5 to 3,5 bbp) is normally adequate initially. The
concentration of PHPA in system should normally be kept in excess at 0,5 to 1,5
kg/m3(0,2 to 0,5 ppb). Calcium should be kept below 200 mg/l.